1. Field of the Invention
This invention relates to a method for removing mercury from a hydrocarbon compound which contains a small amount of mercury and can be handled in a liquid state on a commercial scale (to be referred to as "liquid hydrocarbon compound" hereinafter).
2. Description of Related Art
In the prior art, mercury removal techniques were developed and established as one of the pollution control measures in order to remove toxic mercury from exhausted gases. A variety of techniques were available in the prior art for removing mercury from water and gases.
Palladium-carrying alumina and similar catalysts are often used in modifying a liquid hydrocarbon compound through hydrogenation or the like. It is known that, if mercury is present in the hydrocarbon compound as an incidental impurity, the catalyst is poisoned such that modification may not fully take place.
For removal of mercury from a liquid hydrocarbon compound, there are currently available no techniques which can be practiced on a commercial large scale at a reasonable cost. For example, Japanese Patent Application Kokai No. 90502/1977 discloses a method for removing mercury from vacuum pump oil by adding zinc sulfide to the oil, allowing the zinc sulfide to adsorb and collect mercury, and thereafter separating the mercury along with the excess zinc sulfide. This mercury removal results in a vacuum pump oil having a mercury concentration of about 5 to 3 parts by weight per million parts by volume, but this mercury removal is still insufficient for the object contemplated in the present invention.